Rule of thumb · ComputersNº 80 / 96

Your ISP plan is a ceiling, not a promise

A "500 Mbps" plan means up to 500 Mbps under ideal conditions — not a guaranteed floor. Peak-hour congestion, Wi-Fi, and distance from the local exchange all pull real speeds below the advertised number.

Why it works

Advertised broadband speeds are marketed as maximums by design, and the gap between plan speed and measured speed usually isn’t a fault — it’s Wi-Fi range, a shared neighbourhood connection at busy hours, or simply a different route than the one used for marketing numbers.

Do it exactly

Estimate with the rule, then check it against the calculator that models it properly.

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